This invention relates to data processing methods and systems. More particularly, this invention relates to database generation, management, and handling programs and systems which are capable of multitask processing.
As used in this disclosure, the term data base management refers to computer programs and systems which are capable of receiving items of data which relate to defined fields; storing those items in data files structured in accordance with systematic rules or procedures; permitting access to the files for correction, updating and the like; and permitting access to the files for the generation of reports. The term multitask processing or multitasking refers to the capability of a computer system to handle or permit more than one operator and/or more than one particular program to interact with the system and the data files stored in the system at any one time.
Database management systems and computer programs or software are well known, and are available for use on data processing systems ranging in size from the very large to desktop personal computers. While the difficulties and problems encountered in using such systems and programs will vary with the specific program and the machine environment in which the programs are run, there are at least certain problems which are commonly encountered. For purposes of understanding the present invention, certain of those problems and the manner in which they are avoided or overcome by this invention will be pointed out hereinafter with particular reference to one environment. However, it is to be understood at the outset that this invention contemplates that the improvements here described may be effective in other environments.
At the time of the writing of this disclosure, computer users who face the necessity of processing large volumes of data conventionally use machines known as "mainframes", which are relatively large and powerful machines capable of multitasking and typically having a number of terminals from which access to the central processor and the the data files stored under the control of the central processor may be obtained. Typically, such an environment will use a data management system or facility through which a user can define the form of data files and under which specific programs which manipulate the data stored in the files for specific purposes may operate. For mainframes provided by International Business Machines Corporation ("IBM"), a data management facility or database management program which is in wide use is that known as DB2. Where DB2 is in use, application programs are executed using a System Query Language or SQL. Such applications programs may, for example, deal with such issues as entering invoice information; updating price or inventory information; preparing reports of sales by customer or salesperson identification; billing; and a number of other definable functions. In a typical large data processing center using equipment and programs as here described, application programs to achieve particular purposes may be acquired or written to achieve the particular results intended.
In the environment described, a Time Sharing Option or TSO is often used to enable batch programs which access datafiles of a system to be run. Executing programs under TSO, as distinguished from executing them "natively" or simply within the hierarchy established by the environment, gives rise to difficulties in that such programs incur memory allocations which natively executed programs do not. Further, should the program end abnormally ("abend") for any reason, files may be left improperly disposed and the abend may not be readily recognizable. Should an attempt be made to record execution statistics for evaluating the program operation, then such data are recorded under TSO in a way which does not give assurance that the data are properly linked to the program which has operated. Finally, if operated in an environment where the operating system for the data processing system provides for the possibility of a checkpoint/restart facility, executing a program under TSO will block access to that facility.